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Home Q & A Board Science-Related Homework Help Physics
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smmunday smmunday
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11 years ago
Assuming that radiation with lambda = 15.0 cm is used, that all the energy is converted to heat, and that 4.184 J is needed to raise the temperature of 1.00 g of water by 1.00 C, how many photons are necessary to raise the temperature of a 300 mL cup of water from 20 C to 95 C?
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nusrse2014nusrse2014
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11 years ago
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#2
11 years ago
energy of radiation = (planck's constant * speed of light) / wavelength

planck's constant = 6.62 x 10^-34
speed of light = 3 x 10^8
wavelength = 15 cm = 0.15 m

energy of radiation = (6.62 x 10^-34 x 3 x 10^8) / 0.15 = 1.324 x 10^-24 joules per photon

that is the energy of one photon because photons behaves both particle like and wave like

energy to heat water = water's specific heat x mass x (final temperature - initial temperature)
energy to heat water = 4.184 x 300 x 75 = 94140 joules

94140 / (1.324 x 10^-24) = 7.11 x 10^28 photons
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#3
3 years ago
thank you
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#4
3 years ago
Thank you
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